The California Department of State Hospitals and Department of Public Health collaborated to develop infection control programs in five inpatient psychiatric hospitals in response to COVID-19. In the retrospective observational study described here, conducted from March 2020 through February 2023, we calculated seven-day rolling averages of COVID-19 cases overlaid with key interventions, communication strategies, and policies implemented to break down silos for a consistent and coordinated response. Our findings may inform others regarding effective strategies and partnerships with public health experts during future outbreaks. (Am J Public Health. Published online ahead of print October 3, 2024:e1-e5. https://doi.org/10.2105/AJPH.2024.307846).